Systems are known which facilitate access to databases of information while managing incoming and outgoing calls of a telephone communication system. Such systems typically comprise a host computer with mass storage capabilities for maintaining database information. A protocol converter facilitates conversion of synchronous data output from the host computer for manipulation and use on asynchronous terminals which access the host computer locally and which are coordinated by one or more port controllers.
A call management and database access system such as disclosed in U.S. Pat. No. 4,817,130 further incorporates a local processor which controls a telephone line control unit (LCU) that controls a plurality of lines connected between local switching means and the LCU. Typically the local processor has means for playing a recorded message to provide a voice response to the LCU and a calling party; means for generating and recognizing DTMF (touchtone) signals; and means for controlling the port controllers to control connection of the terminals to the local processor or to the protocol converter for communication with the host computer. Known systems, however, are of limited efficiency because limited database information is available to an intervening human operator so that the operator must re-initiate a- dialogue with a caller and then request database information via a local terminal.
In known systems, such as generally illustrated in FIG. 1A, communication between a host and a terminal or other device such as a printer, requires that all the equipment involved be capable of communication via an appropriate communication protocol as known in the art, such as SDLC or BISYNC. Protocol conversion is required, typically at the local processor or system controller level (C1), so that the asynchronous terminal (T) or device can use the information communicated by a synchronous port of the host processor(s). Information issued from the host is packaged, i.e. in SDLC in a "frame", with coded fields for identification, control and verification. The coded information must be unpackaged from the information usable by the asynchronous terminal. The unpackaging of data or information from the host to send to an asynchronous terminal and the packaging of data received from an async terminal to send to the host, is generally performed by a controller (Cl) having protocol conversion capabilities. The controller typically operates under host program control and considerable controller overhead can be required in packaging and unpackaging information transfers, negatively impacting the host.
As illustrated in FIG. 1B, a plurality of terminals (Tl-Tn) or devices can access and be accessed through a controller (C2) via a single synchronous port (P1) of a synchronous host, which processes a packet or frame of information according to a particular protocol. When it is desired to access and receive information at a remote terminal (Tra) asynchronously from a host port (P2) via a telecommunications modem (M1, M2), an entire synchronous port of the host is occupied. Accordingly, the waste of resources can be significant. For instance, if the single synchronous port (P2) was capable of communicating with 8 terminals, the entire 8-terminal port would have to be dedicated to a modem for transmission even if only one terminal was desired for remote access. Such a configuration results in inefficient and costly allocation of resources, in addition to considerable processor overhead.
Further, where it is desired to access and receive information at a terminal (Trs) synchronously from a host port (P3) via a telecommunications modem (M1, M2) a controller (cont) at the remote cite is necessary to provide the protocol conversion. A required dedicated controller, in communication with the remote synchronous terminal Trs is an expensively inefficient hardware implementation.